A magnetic disk drive is known as an information processing device, during a falling, which can perform an operation for receiving a shock at the end of the falling and which can improve a shock resistance.
In conventional arts, there is a magnetic disk drive provided with a protection function, which can protect itself from data loss or off tracks by detecting a vibration and so on with an accelerometer, by interrupting writing operation before data are written at an off-track position. However, this protection function is not so effective as to alleviate a collision shock that derives from a free falling of the magnetic disk drive.
An acceleration of the free falling is only one gravity. One gravity is not enough for such prior sensor to activate the protection function that the prior sensor can start to act with two to ten times of gravity. And if the protection function would not start, magnetic heads be still on magnetic disks, which would cause severe physical damage on the magnetic disks. Therefore, in the present technique when magnetic disk drives are given with shocks while magnetic heads are positioned on the magnetic disks, damage tolerance depends simply on a strength of the magnetic heads and the magnetic disks.
While there are magnetic disk drives having accelerometer devices to detect falling state, there are other magnetic disk drives having a simple-structure sensor without complicated electronic circuits. As an example of such simple structure, JP-A-8-29450 discloses a magnetic disk drive, which is provided with a status sensor having a conductive sphere that is sealed within a cavity in order to detect whether the magnetic disk drive is in unstable state, and before shocks attack the drive which can prepare a countermeasure operation preventing erroneous operation.
In a conventional art, a shock-detecting sensor is activated immediately after the shock is incurred at the end of the falling of a magnetic disk drive. Instantaneous shock-avoiding operation of such drive as an interruption of read/write operation with data to magnetic disk media can minimize damages to some extent.
Regarding to the physical damage by the clash of magnetic heads and so on to a surface of the magnetic disk media, which is caused by a vertical shock to the surface of the magnetic disks, the activation of the sensor incurred after the shock cannot avoid such vertical damage because there is not enough time for the magnetic heads to move from a position on the media to an outside position of the media. Therefore, the prevention of the damage depended on the strength of the magnetic heads and the magnetic disks.
The method of detecting the falling by an acceleration sensor device requires an expensive high-sensitivity analog output sensor. This kind of a sensor is so vulnerable to the erroneous operation with noise that a vector arithmetic processing is inevitable. And it needs complicated electric circuits for the erroneous operation and additional amplifying circuits.
The JP-A-8-29450 discloses a status sensor having a sphere sealed within a cavity. At a free-falling state with zero initial speed, the sphere is adhered to a wall surface of the cavity, therefore the falling state cannot be detected. As the sphere can travel inside the cavity freely, the falling state cannot be accurately detected.
The present invention objects to offer a simple-structure sensor which can sense falling including a free falling using a simple method. The present invention also offers to improve a shock tolerance of a magnetic disk drive or an information processing device by mounting the sensor on them. The present invention also offers an information processing device having this sensor, which performs during a falling anti-shock operation for the end of the falling, for example, a magnetic disk drive moving or evacuating magnetic heads from surface of magnetic disk media, or another information processing device having such magnetic disk drive. They have high shock tolerance because of enabling magnetic heads to evacuate from the surface of the magnetic disk media, while the magnetic disk drive or the information processing device goes into falling state before the end of the falling.